Polarizing sheets made of an aromatic polycarbonate have excellent impact resistance and are light, and therefore are used for liquid crystal displays as well as windows of buildings, sunroofs of cars, etc.
Further, polarizing sheets, which are obtained by laminating an aromatic polycarbonate sheet as a protection layer through an adhesive layer to each surface of a polarizing sheet obtained by stretching a polyvinyl alcohol film and staining it with a dichroism pigment (hereinafter referred to as “aromatic polycarbonate polarizing sheet”), particularly have excellent impact resistance and also have high heat resistance, and therefore are used for polarizing lenses for eyewear (sunglasses, goggles, etc.) to be used for marine sports, winter sports, fishing, etc. obtained from a curving process or injection molding process.
However, since aromatic polycarbonate has a high photoelastic constant, when a curving process is applied to a spherical or aspherical shape of sunglasses, goggles or the like, a coloring interference stripe (iridescent pattern) tends to easily occur due to retardation. Such a coloring interference stripe causes poor outer appearance of a polarizing lens, and this is a major problem particularly in the field of eyewear in which the beauty of outer appearance affects purchasing power for products. Moreover, such a coloring interference stripe also has a problem that health problems such as eye strain are caused thereby.
Regarding handling of retardation caused at the time of applying a curving process, an aromatic polycarbonate polarizing sheet, whose coloring interference stripe has been hidden from view by subjecting an aromatic polycarbonate sheet to be used for a protection layer to a stretching process to cause a large retardation in advance (hereinafter referred to as “stretched polycarbonate polarizing sheet”), is known (Patent Document 1).
However, when using the stretched polycarbonate polarizing sheet, it is possible to prevent occurrence of a coloring interference stripe, but since the aromatic polycarbonate sheet has been stretched, the aromatic polycarbonate is contracted in the stretching direction at the time of the curving process, and the absolute value of the difference between the base curve in the vertical direction and the base curve in the horizontal direction of the formed polarizing lens (hereinafter referred to as “base curve anisotropy”) increases, causing the problem of reduction in the resolution of the lens.
Meanwhile, a polarizing lens, which is formed by subjecting the afore-mentioned stretched polycarbonate polarizing sheet to a curving process to provide a spherical or aspherical shape, inserting the resultant stretched polycarbonate polarizing sheet into a mold and injecting an aromatic polycarbonate thereto, for the purpose of improving impact resistance to be more than that of a polarizing lens formed by subjecting the afore-mentioned stretched polycarbonate polarizing sheet to a curving process or forming a corrective lens having a focal refractive power, is known (Patent Documents 2 and 3). However, the problems of occurrence of a coloring interference stripe and the resolution have not been solved even by such a polarizing lens.
Further, a method of using an aromatic polycarbonate sheet in which the stretch thereof has been eliminated or decreased on the concave surface side for the purpose of preventing occurrence of a coloring interference stripe at the time of the curving process and improving the curved shape is also known (Patent Document 3). However, even in this case, a stretched aromatic polycarbonate sheet is used on the convex surface side, and therefore, reduction in the resolution due to the curved shape base curve anisotropy is not improved sufficiently.
It is known that a film comprising a polycarbonate resin, which is obtained by carbonate bonding two types of components that are 99 to 5 mol % of a compound represented by general formula (1) below and 1 to 95 mol % of a dihydroxy compound other than that using a carbonic acid diester, is an optical film having good balance between low birefringence, high transparency and high glass-transition temperature (see Patent Document 4). Further, a polarizing sheet in which such a film is used as a protection film for the polarizing sheet of a flat panel display has been reported (see Patent Document 5), but use of such a polarizing sheet comprising a special polycarbonate resin as a polarizing sheet for a polarizing lens to be subjected to a curving process has not been studied.
